1. Field of the Art
This invention relates to a seal construction suitable for use in a valve assembly, and more particularly to a seal construction suitable for use in hermetically joining a manifold base, which contains a plural number of fluid inlet and outlet passages, with a casing of a change-over valve which is operated to switch fluid flows through the fluid inlet and outlet passages in the manifold base.
2. Prior Art
For example, it has been well known in the art to assemble a change-over valve mechanism on a manifold base which contains a plural number of fluid inlet and outlet passages, for the purpose of supplying and discharging pressurized air or other pressurized fluid medium indirectly through the manifold base instead of directly feeding the pressurized air to and from inlet and outlet ports on the change-over valve mechanism through separate pipes. In a valve assembly of this sort, a gasket is usually provided between the manifold base and the change-over valve as a seal to prevent leaks of the pressurized air.
The conventional gaskets which serve for the above-mentioned purpose are generally of a flat sheet-like form with planar surfaces, and designed to be gripped and clamped between flat joining surfaces of a manifold base and a change-over valve casing. Therefore, if a stronger force is imposed on a certain locality of the gasket while being set into a clamped position, it is very likely for the gasket to undergo deformation or positional deviation, making it difficult to set it correctly in a predetermined seal position and often resulting in sealing failures. Similarly, conventional gaskets are apt to undergo deformations or deviations when a high air pressure is applied thereto from a lateral direction, increasing the possibilities of leaks of the pressurized fluid.
The problems of positional deviations and deformations of a gasket can be prevented by fitting same in shallow grooves which are formed on the joining surfaces of the manifold base and the change-over valve casing. However, generally gaskets are very thin in thickness, so that, without sophisticated high-tech facilities, it is extremely difficult to form shallow grooves which are capable of compressing a thin gasket to such a degree as to guarantee a tight seal while holding it securely in a predetermined seal position against deviations and deformations. In addition, as long as a flat gasket is clamped between flat joining surfaces, it makes no significant difference from a gasket which is clamped between joining surfaces without grooves, giving rise to the same difficulties in securing a high sealing strength.